Display apparatus and driving method thereof

ABSTRACT

A display apparatus including a plurality of gate lines, a data line intersecting the plurality of gate lines; a first pixel unit connected with a n-th gate line of the plurality of gate lines and the data line. A second pixel unit connected with a (n+1)-th gate line of the plurality of gate lines; and a coupling capacitor disposed between the first pixel unit and the second pixel unit, wherein the first pixel unit comprises a first liquid crystal capacitor and a first thin film transistor (TFT), the second pixel unit comprises a second liquid crystal capacitor and a second thin film transistor (TFT), and a source electrode and a drain electrode of the second TFT are connected with both electrodes of the coupling capacitor, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/077,496 filed on Mar. 18, 2008, which claims priority from KoreanPatent Application No. 10-2007-0065452 filed on Jun. 29, 2007, in theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display apparatus and a drivingmethod thereof

2. Description of the Related Art

Liquid crystal displays (LCD) are one of the most widely used flat paneldisplays. An LCD typically includes two panels provided withfield-generating electrodes such as pixel electrodes and a commonelectrode, and a liquid crystal (LC) layer interposed therebetween. TheLCD displays images by applying voltages to the field-generatingelectrodes to generate an electric field in the LC layer. The appliedelectric field determines the orientations of LC molecules in the LClayer to adjust the polarization of incident light.

The LCD comprises a plurality of thin film transistors (TFT) connectedwith each of the pixel electrodes and a plurality of signal linesconnected with the TFTs, such as gate lines and data lines.

Among the LCDs, a vertically aligned (VA) LCD, in which LC molecules arealigned such that the long axes of the LC molecules are perpendicular tothe plates in the absence of an electric field, offers a high contrastratio and a wide reference viewing angle. The reference viewing angle isdefined as a viewing angle making the contrast ratio equal to 1:10 or asa limit angle for the inversion in luminance between the grays.

A wide viewing angle of the VA mode LCD can be realized by, for example,cutouts in the field-generating electrodes and protrusions on thefield-generating electrodes. The cutouts and the protrusions candetermine the tilt directions of the LC molecules. The tilt directionscan be distributed in several directions by using the cutouts and theprotrusions such that the reference viewing angle can be widened.

However, the cutouts and the protrusions decrease the aperture. Also,the lateral visibility of the VA mode LCD is low. For example, imagesdisplayed by a patterned vertically aligned (PVA) LCD equipped with thecutouts become brighter nearer to the lateral sides of the PVA LCD,thereby decreasing lateral visibility.

In order to improve lateral visibility of an LCD, a variety of methodsof dividing a pixel electrode into a pair of sub-pixel electrodes,applying voltage to the one sub-pixel electrode using thin filmtransistor (TFT) and applying voltage to the other sub-pixel electrodeusing a coupling capacitor so that the sub-pixel electrodes can besupplied with different voltages have been suggested.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a display apparatus havingexcellent lateral visibility without image sticking

Aspects of the present invention also provide a driving method of adisplay apparatus having excellent lateral visibility without imagesticking

However, the aspects of the present invention are not restricted to onesset forth herein. The above and other aspects of the present inventionwill become apparent to one of ordinary skill in the art to which thepresent invention pertains by referencing the detailed description ofthe present invention given below.

According to a first aspect of the present invention, there is provideda display apparatus including: a plurality of gate lines; a data lineintersecting the plurality of gate lines; a first pixel unit connectedwith a n-th gate line of the plurality of gate lines and the data line;a second pixel unit connected with a (n+1)-th gate line of the pluralityof gate lines; and a coupling capacitor disposed between the first pixelunit and the second pixel unit, wherein the first pixel unit comprises afirst liquid crystal capacitor and a first thin film transistor (TFT),the second pixel unit comprises a second liquid crystal capacitor and asecond thin film transistor (TFT), and a source electrode and a drainelectrode of the second TFT are connected with both electrodes of thecoupling capacitor, respectively. One electrode of the first liquidcrystal capacitor and one electrode of the coupling capacitor are formedof a first pixel electrode. Here, the first pixel electrode is formed oftransparent metal. One electrode of the second liquid crystal capacitorand the other electrode of the coupling capacitor are formed of a secondpixel electrode. Here, the second pixel electrode is formed oftransparent metal.

The display apparatus further comprises a plurality of storage electrodelines, wherein the first pixel unit comprises a storage capacitorconnected with the n-th storage electrode line of the plurality ofstorage electrode lines and the first TFT. Here, a storage-capacitancevoltage applied to the n-th storage electrode line has a fixed orvariable level.

According to a second aspect of the present invention, there is provideda display apparatus including: a plurality of gate lines; a data lineintersecting the plurality of gate lines; a first pixel unit connectedwith a n-th gate line of the plurality of gate lines and the data line,comprising a first liquid crystal capacitor and a first thin filmtransistor (TFT); a second pixel unit connected with the n-th gate lineand the data line, comprising a second liquid crystal capacitor and asecond thin film transistor (TFT); and a third thin film transistor(TFT) connected with the (n+1)-th gate line of the plurality of gatelines and second pixel unit, wherein a coupling capacitor is disposedbetween a drain electrode of the second TFT and one electrode of thesecond liquid crystal capacitor. A gate electrode of the third TFT isconnected with the (n+1)-th gate line, a source electrode of the thirdTFT is connected with the drain electrode of the second TFT and oneelectrode of the coupling capacitor, a drain electrode of the third TFTis connected with the one electrode of the second liquid crystalcapacitor and the other electrode of the coupling capacitor. Here, thefirst pixel unit further comprises a first storage capacitor, and oneelectrode of the first liquid crystal capacitor and one electrode of thefirst storage capacitor are formed of a first pixel electrode.

The display apparatus further comprises a plurality of storage electrodelines, wherein the other electrode of the first is connected with a n-thstorage electrode line of the plurality of storage electrode lines.Here, a storage-capacitance voltage applied to the n-th storageelectrode line has a fixed or a variable level. The second pixel unitfurther comprises a second storage capacitor, and the one electrode ofthe second liquid crystal capacitor, the one electrode of the secondstorage capacitor and the other electrode of the coupling capacitor areformed of a second pixel electrode. Here, the second pixel electrode isformed of transparent metal.

According to a third aspect of the present invention, there is provideda driving method of a display apparatus including: applying a datavoltage to a first pixel unit and a second pixel unit connected with thefirst pixel unit through a coupling capacitor, and discharging thecoupling capacitor. Here, the discharging of the coupling capacitorcomprises providing electric charge in the coupling capacitor to thesecond pixel unit. When the first pixel unit and the second pixel unitare connected with a first gate line, the applying of a data voltage isenabled by a first gate signal applied to the first gate line, and thedischarging of the coupling capacitor is enabled a second gate signalapplied to a second gate line. The first pixel unit comprises a firstliquid crystal capacitor including a first pixel electrode and a commonelectrode, and a first storage capacitor including the first pixelelectrode and a storage-capacitance electrode, and the applying of adata voltage comprises applying a storage-capacitance voltage having afixed level to the storage-capacitance electrode, or the applying a datavoltage comprises applying a storage-capacitance voltage having avariable level to the storage-capacitance electrode.

Details of other embodiments of the invention are included in thedetailed description of the invention and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a liquid display apparatusaccording to an exemplary embodiment of the invention;

FIG. 2 is a pictorial, perspective diagram illustrating a pixel of thetype employed in FIG. 1;

FIG. 3 is an equivalent a circuit diagram of the a pixel of a liquiddisplay apparatus according to an embodiment of the invention;

FIG. 4 is a signal diagram illustrating signals of the type used in anoperation of a pixel of the type illustrated in FIG. 3; and

FIG. 5 is an equivalent circuit diagram of a pixel of a liquid displayapparatus according to another exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Advantages and features of the present invention and methods ofaccomplishing the same may be understood more readily by reference tothe following detailed description of exemplary embodiments and theaccompanying drawings. The present invention may, however, be embodiedin many different forms and should not be construed as being limited tothe exemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the concept of the invention to those ofordinary skill in the art, and the present invention will only bedefined by the appended claims.

FIG. 1 is a block diagram of a liquid crystal display apparatusaccording to an exemplary embodiment of the invention, and FIG. 2 is adiagram illustrating the type of pixel utilized in the FIG. 1embodiment.

Referring to FIG. 1, the liquid crystal display apparatus according toan exemplary embodiment of the invention includes a liquid crystal panelassembly 300, a gate driver 400, a data driver 500, a gray-voltagegenerator 800, and a signal controller 600.

In the an electrical equivalent circuit, the liquid crystal panelassembly 300 includes a plurality of display lines G1 through Gn and D1through Dm, and a plurality of pixels PX connected to the plurality ofdisplay lines G1 through Gn and D1 through Dm and arranged in a matrix.Referring to FIG. 2, the liquid crystal panel 300 includes a firstsubstrate 100 and a second substrate 200 facing each other, and a liquidcrystal 3 interposed between the first and second substrates 100 and200.

Signal lines comprise a plurality of gate lines for transmitting gatesignals (also called “scan signals”), and a plurality of data lines D1through Dm for transmitting data signals. The plurality of gate lines G1through Gn extend in a row direction and are parallel or essentiallyparallel to one another, and the plurality of data lines D1 through Dmextend in a column direction and are parallel or essentially parallel toone another.

Each of pixels PX comprises a pair of pixel units, and each of the pixelunits comprises liquid crystal capacitors Clca and Clcb, respectively.At least one of the pixel units comprise a gate line, data line, andswitching element (not shown) connected with liquid crystal capacitorClca or Clcb.

The liquid crystal capacitors Clca, Clcb have pixel unit electrodes PEaand PEb formed on the first substrate 100 and a common electrode CEformed on the second substrate 200, respectively, as two electrodes. Theliquid crystal layer disposed between the pixel unit electrodes PEa andPEb and the common electrode 270 functions as a dielectric. The pair ofpixel unit electrodes PEa and PEb are separated from each other, andmake one pixel electrode PE.

The common electrode CE is connected to the common voltage Vcom, andcovers the entire surface of the second substrate 200. The liquidcrystal layer 3 has negative dielectric anisotropy (Δε<0), i.e., thelong axes of the liquid crystal molecule are aligned vertically withrespect to a field-generating direction. Alternatively, the commonelectrode 270 may disposed on the first substrate 100, and, in thiscase, at least one of the pixel electrode PE and the common electrode270 may have shapes resembling bars or stripes.

For a color display, each pixel PX uniquely represents one of threeprimary colors such as red, green and blue (R, G and B) colors (spatialdivision) or sequentially represents the three primary colors in time(temporal division), thereby obtaining a desired color. FIG. 2 is anequivalent circuit diagram of a spatial division. A color filter CF maybe formed in a portion of a common electrode CE of the second substrate200.

One or more polarizers (not shown) may be attached to at least one ofthe first substrate 100 and the second substrate 200 to transform lightpolarization into light transmittance.

The gamma voltage generator 800 generates two sets of a plurality ofgray voltages related to the transmittance of the pixels. The datavoltages in one set have a positive polarity with respect to the commonvoltage Vcom, while those in the other set have a negative polarity withrespect to the common voltage Vcom. The positive-polarity data voltagesand negative-polarity data voltages are alternately supplied to theliquid crystal panel 100 during inversion driving.

The gate driver 400 is connected to the gate lines G1 -Gn of the liquidcrystal panel assembly 300, and applies gate signals from an externaldevice to the gate lines G1-Gn, each gate signal being a combination ofa gate-on voltage Von and a gate-off voltage Voff.

The data driver 500 is connected to the plurality of data lines D1-Dm ofthe liquid crystal panel assembly 300. The data driver 500 generatesgray voltages based on a plurality of voltages supplied from the gammavoltage generator 800, selects the generated gamma voltages, and appliesthe gamma voltages to each pixel as data signals.

The signal controller 600 controls the gate driver 400 and the datadriver 500.

The gate driver 400, the data driver 500 or the gamma voltage generator800 may be directly mounted on the liquid crystal panel assembly 300 inthe form of at least one IC chip on the liquid crystal panel assembly300. Alternatively, the gate driver 400 or the data driver 500 may beattached to the liquid crystal panel 300 in the form of a tape carrierpackage (“TCP”) on a flexible printed circuit (“FPC”) film (not shown)in the liquid crystal panel assembly 300. Alternatively, the gate driver400 or the data driver 500 together with the plurality of display linesG1 through Gn and D1 through Dm, and switching devices Q may beintegrally formed with the liquid crystal panel assembly 300.

FIG. 3 is an equivalent a circuit diagram of a pixel of a liquid displayapparatus according to an embodiment of the invention.

The liquid crystal panel assembly 300 comprises the plurality of gatelines GL, and the data line DL, and pixels PX coupled to associated onesgate line GL and the data lines DL.

The pixel PX comprises the pair of the first pixel unit main, and thesecond pixel unit sub, and the coupling capacitor C_cp connected betweenthe first pixel unit main and the second pixel unit sub.

The first pixel unit main comprises a first TFT TFT1 connected with then-th gate line GL and the data line DL, a first liquid crystal capacitorH_lc connected with the first TFT TFT1, and the first storage capacitorH_cst connected with the first TFT TFT1. The second pixel unit subcomprises the second TFT TFT2 connected with the (n+1)-th gate line GL,the second liquid crystal capacitor L_lc connected with the first TFTTFT1, and the second storage capacitor L cst connected with the secondTFT TFT2.

The coupling capacitor C_cp is disposed between the first pixel unitmain and the second pixel unit sub. However, only one of the firststorage capacitor H_cst and the second storage capacitor L_cst may bedisposed.

One electrode of first liquid crystal capacitor H_lc and one electrodeof the first storage capacitor H_cst may be formed of a transparentfirst pixel electrode, and one electrode of the second liquid crystalcapacitor L_lc and one electrode of the second storage capacitor L_cstmay be formed of a transparent second pixel electrode. Also, oneelectrode of the coupling capacitor C_cp may be formed of the firstpixel electrode, and the other electrode of the coupling capacitor C_cpmay be formed of the second pixel electrode.

Explaining the operation of the pixel, first, the first TFT TFT1provides a data voltage with the first pixel electrode responding to thegate signal applied to the n-th gate line. The first pixel unit voltage,that is, the voltage applied to the first liquid crystal capacitor H_lcis provided with the second pixel unit sub by the coupling capacitorCcp. When the voltage of the first liquid crystal capacitor H_lc is Va,and the voltage of the second liquid crystal capacitor L_lc is Vb, thenVb is given by Equation 1 below.

Vb=Va×(C _(—) cp/(C _(—) cp+L _(—) lc+L _(—) cst))   (1)

Because the value of C_cp/(C_cp+L_lc+L_cst) is less than 1, the voltageVb of the second liquid crystal capacitor L_lc is less than Va of thefirst liquid crystal capacitor H_lc.

The voltages Va and Vb are controlled by varying the capacitance of thecoupling capacitor C_cp. The transmittance of the liquid crystal isdetermined by the voltage Vb of the second liquid crystal capacitor L_lcand than the voltage Va of the first liquid crystal capacitor H_lc, andthen an image is displayed according to the transmittance.

Next, the second TFT TFT2 is turned on by a gate signal applied to the(n+1)-th gate line GL. When the second TFT TFT2 is turned on, thecoupling capacitor C_cp is discharged. That is, the charge of thecoupling capacitor C_cp may be provided with the second liquid crystalcapacitor L_lc. For example, if the positive data voltage is providedwith the first liquid crystal capacitor H_lc and the second liquidcrystal capacitor L_lc, the charge of the coupling capacitor C_cp may beprovided with the second liquid crystal capacitor L_lc, and then thelevel of the voltage of the second liquid crystal capacitor L_lc isincreased.

Here, the level of the voltage of the second liquid crystal capacitorL_lc by discharging of the coupling capacitor C_cp when the data voltagehaving high gray is provided is higher than that when the data voltagehaving low gray is provided. That is, the difference between the voltageVa and the voltage Vb when the data voltage having high gray is providedis higher than that when the data voltage having low gray is provided.Therefore, the lateral visibility of the display apparatus is improved.

Also, if the second TFT TFT2 is turned on, a path is formed throughwhich charges produced at node A move. Thus, charge is not accumulatedat node A, and image sticking can be reduced.

Here, if the ratio of channel width to channel length W/L of the secondTFT TFT2 is very large, the voltage difference between both nodes of thecoupling capacitor C_cp will be zero, and then the voltage Va of thefirst liquid crystal capacitor H_lc and voltage Vb of the second liquidcrystal capacitor L_lc will be the same, so the lateral visibility ofthe display apparatus will not be improved. Thus, it is preferable thatthe ratio of channel width to channel length W/L of the second TFT TFT2should not be very large.

The other electrode of the first storage capacitor H_cst is connectedwith the n-th storage electrode line SL, and a storage-capacitancevoltage applied to the n-th storage electrode line SL may have a fixedlevel. The storage-capacitance voltage may be the common voltage Vcomapplied to the common electrode CE.

Also, the storage-capacitance voltage may have a variable level, forexample, the level of the storage-capacitance voltage may varyperiodically. The storage-capacitance voltage will now be described indetail with reference to FIG. 4.

The data voltage applied to the data line DL, the storage-capacitancevoltage applied to the storage electrode line SL, and the voltage of thefirst liquid crystal capacitor H_lc are shown in FIG. 4. For explanatoryconvenience, it is assumed that the polarity of the data voltage varieswith respect to the common voltage Vcom frame by frame.

Referring to FIG. 4, when the polarity of the data voltage varies withrespect to the common voltage Vcom, the polarity of thestorage-capacitance voltage varies identically with the polarity of thedata voltage. For example, when the data voltage is positive withrespect to the common voltage Vcom, the storage-capacitance voltage ispositive with respect to the common voltage Vcom, and when the datavoltage is negative with respect to the common voltage Vcom, thestorage-capacitance voltage is negative with respect to the commonvoltage Vcom.

When the storage-capacitance voltage varies, the voltage of the firstliquid crystal capacitor H_lc connected with the first storage capacitorH_cst varies as shown FIG. 4. For example, the voltage of the firstliquid crystal capacitor H_lc may be equal to the sum of the datavoltage and the storage-capacitance voltage.

As described above, if the storage-capacitance voltage varies, thevoltage of first liquid crystal capacitor H_lc may be the predeterminedvoltage that is higher than the data voltage applied to the data lineDL. Also, if the voltage of the first liquid crystal capacitor H_lcincreases, the voltage of the second liquid crystal capacitor L_lcincreases. In this case, the transmittance of the pixel units main andsub may be improved.

A display apparatus according to a second embodiment of the presentinvention is illustrated in FIG. 5 which is an equivalent circuitdiagram of a pixel of a liquid display apparatus according to the secondembodiment of the invention.

The display apparatus according to the second embodiment of the presentinvention further comprises a third TFT TFT3 for controlling theoperation of the second liquid crystal capacitor L_lc. In contrast tothe prior embodiment, the coupling capacitor C_cp is not directlyconnected with the first liquid crystal capacitor H_lc, but rather isconnected with the third TFT TFT3.

More specifically, each pixel PX comprises a main pixel unit and asub-pixel unit. The main pixel unit and sub-pixel unit are connectedwith the n-th gate line GL of the plurality of gate lines and to dataline DL. The main pixel unit comprises a first liquid crystal capacitorH_lc , first storage capacitor H_cst and a first TFT TFT1 connected withthe n-th gate line GL. The sub-pixel unit comprises a second liquidcrystal capacitor L_lc , a second storage capacitor L_cst, the third TFTTFT3 connected with the n-th gate line GL, and a coupling capacitorC_cp.

The gate electrode of fourth TFT TFT4 is connected with the (n+1)-thgate line GL, the source electrode of fourth TFT TFT4 is connected withthe drain electrode of third TFT TFT3 and to one electrode of thecoupling capacitor C cp, and the drain electrode of a fourth TFT TFT4 isconnected with the one electrode of the second liquid crystal capacitorL_lc and the other electrode of the coupling capacitor C_cp. Oneelectrode of the first liquid crystal capacitor H lc and one electrodeof the first storage capacitor H_cst may be formed of a transparentfirst pixel electrode. One electrode of the second liquid crystalcapacitor L_lc and one electrode of the second storage capacitor L_cstmay be formed of a transparent second pixel electrode.

The operation of the pixel illustrated in FIG. 5 is as follows. When agate signal is applied to the n-th gate line GL, the first TFT TFT1 andthe third TFT TFT3 are turned on. Therefore, the first liquid crystalcapacitor H_lc is charged to the data voltage. Also, the data voltage isdivided by the coupling capacitor C_cp and the second liquid crystalcapacitor L_lc, and then the voltage on second liquid crystal capacitorL_lc becomes a predetermined value.

Next, when a gate signal is applied to the (n+1)-th gate line, thefourth TFT TFT4 is turned on. Thus the coupling capacitor C_cp isdischarged. Therefore, the charges of the coupling capacitor C_cp can beprovided to the second liquid crystal capacitor L_lc, and the lateralvisibility of the display apparatus is improved.

Also, when the third TFT TFT3 is turned on, a path is formed throughwhich charges at node A move. Thus, charge is not accumulated at node A,and image sticking is reduced.

In the present exemplary embodiment of the present invention, though thefourth TFT TFT4 is turned on, the data voltage of the first liquidcrystal capacitor H_lc may not vary, because the coupling capacitor C_cpis not connected with the first liquid crystal capacitor H_lc.

The other electrode of the first storage capacitor H cst and the secondstorage capacitor L_cst are connected to the n-th storage electrode lineSL, as a storage-capacitance electrode. Here, a storage-capacitancevoltage applied to the storage-capacitance electrode may have a fixedlevel. The storage-capacitance voltage may be the common voltage Vcomapplied to the common electrode CE.

Also, the storage-capacitance voltage may have a variable level, forexample, the level of the storage-capacitance voltage may varyperiodically, as described above. In this case, the transmittance of thepixel units main and sub may be improved.

To sum up, the display apparatus and the driving method thereofaccording to the exemplary embodiments of the present invention provideexcellent lateral visibility without incurring the image stickingphenomenon.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the present invention which is defined by the following claims. Theexemplary embodiments are descriptive only and not limiting.

1. A display apparatus comprising: a plurality of gate lines; a dataline intersecting the plurality of gate lines; a first pixel unitassociated with an n-th gate line of the plurality of gate lines and thedata line, comprising a first liquid crystal capacitor and a first thinfilm transistor; a second pixel unit associated with the n-th gate lineand the data line, comprising a second liquid crystal capacitor and asecond thin film transistor; a third thin film transistor connected withan (n+1)-th gate line of the plurality of gate lines and second pixelunit; and a coupling capacitor having a first electrode connected to adrain electrode of the second thin film transistor and a secondelectrode connected to an electrode of the second liquid crystalcapacitor.
 2. The display apparatus of claim 1, wherein a gate electrodeof the third thin film transistor is connected with the (n+1)-th gateline, a source electrode of the third thin film transistor is connectedto the drain electrode of the second thin film transistor and the firstelectrode of the coupling capacitor, a drain electrode of the third thinfilm transistor is connected with the one electrode of the second liquidcrystal capacitor and the second electrode of the coupling capacitor. 3.The display apparatus of claim 2, wherein the first pixel unit furthercomprises a first storage capacitor, and one electrode of the firstliquid crystal capacitor and one electrode of the first storagecapacitor are formed of a first pixel electrode.
 4. The displayapparatus of claim 3, wherein the first pixel electrode is formed oftransparent metal.
 5. The display apparatus of claim 3, furthercomprising a storage electrode line, wherein the first storage capacitoris coupled to the storage electrode line.
 6. The display apparatus ofclaim 5, wherein a storage-capacitance voltage applied to the storageelectrode line has a fixed level.
 7. The display apparatus of claim 5,wherein a storage-capacitance voltage applied to the storage electrodeline has a variable level.
 8. The display apparatus of claim 2, whereinthe second pixel unit further comprises a second storage capacitor, andone electrode of the second liquid crystal capacitor, the electrode ofthe second storage capacitor and the second electrode of the couplingcapacitor are formed of a second pixel electrode.
 9. The displayapparatus of claim 8, wherein the second pixel electrode is formed oftransparent metal.